In humans, the gene for thick lips is dominant in relation to the gene for thin lips. In the family

In humans, the gene for thick lips is dominant in relation to the gene for thin lips. In the family, the woman has thin lips, and the man has thick lips. The man’s father had thin lips. How many different genotypes and phenotypes can the children of this married couple have?

Let’s designate the gene for thin lips as l, and the gene for thick lips as L.

A woman with thin lips is ll, because this trait can develop only if the genotype is homozygous for the gene that causes it. Such a woman produces eggs l.

The man’s father had thin lips, therefore, like the woman, he was ll and produced the same type of spermatozoa l. He could pass on to his son only the gene for thin lips, therefore, a man with thick lips is heterozygous – Ll. It produces two types of sperm – L and L.

The offspring of this married couple will be represented by the following options:

children – heterozygotes with thick lips (Ll) – 50%;

children – homozygotes with thin lips (ll) – 50%.